Cellulose has been widely used in the production of sausage skins. In general, known commercial methods for processing cellulose into sausage skins involve exposing raw cellulose (e.g. Cellulose I) to an aqueous alkali solution, and adding complexing agents to produce a cellulose dope. The dope is then subjected to various processing steps to regenerate the cellulose. The cellulose produced by these methods is known as regenerated cellulose because the cellulose molecules are dissolved by the production of specific coordination complexes with the dissolving solvent. For example, according to one method, the raw cellulose is first steeped in sodium hydroxide. Carbon disulfide is then added to the resulting alkali cellulose crumb under specific conditions, resulting in the formation of sodium cellulose xanthanate. This coordination complex is then extruded in a tubular shape into an acid bath which converts the coordination complex into regenerated cellulose in the form of an elongated tubular sausage skin. Typically, sausage manufacturers add plasticizers or other materials in a conventional manner to the process prior to forming the skin.
The tubular skins are then dried, typically by blowing air through their center and along their exterior. The dried skins are then rolled or coiled because conventional sausage machines commonly use the skins in this form. That is, as the skins are uncoiled by the sausage machines, they are filled with the contents to make sausages. Again, these skins may be filled with any suitable edible material, including animal and vegetable food stuffs. Also, the sausage skins may be manually stuffed to form sausages.
During the manufacture of skinless sausages, at some point during the process after the skins are stuffed with their contents, the skin is stripped from the contents. The used sausage skins are then discarded in a landfill or in some cases incinerated. With the large volume of skinless sausages produced in this country, disposal of the used skins is costly and environmentally wasteful.
In the above-described process of producing these skins, the intramolecular hydrogen bonding in the cellulose is disrupted through the formation of coordination complexes between the alkali and the glucose of the cellulose. Two common methods for the production of regenerated cellulose are the viscose method and the cupraammonium method, with the viscose method commonly being employed to produce sausage skins. Each of these methods utilizes expensive materials, and each produces certain toxic by-products. Thus, although these methods have been successfully used for many years, environmental and economic concerns are inherent with each method. In addition, because the glucose moieties of regenerated cellulose produced by either the viscose method or the cupraammonium method exist as a coordination complex, the degree of polymerization of the molecule is reduced. As the number of coordination complexes in the regenerated cellulose increases, the intramolecular hydrogen bond forming sites on the cellulose molecules decrease. This generally decreases the commercial desirability of the resulting sausage skins because an increased number of intramolecular hydrogen bonding sites generally produces higher quality finished products.
It is known that cellulose swells when it is exposed to the hydrogen bond cleaving agent, sodium hydroxide. Swelling in the cellulose by nearly 1,000 percent is achieved upon exposure to sodium hydroxide maintained at soda cellulose Q condition. This is explained in an article by Sobue, et al., entitled "The Cellulose-Sodium Hydroxide-Water System as a Function of Temperature", Z.Physik Chem. (B) 43 (3), 1939. Soda cellulose Q condition occurs when cellulose is in an aqueous solution of 6 percent to 10 percent by weight of sodium hydroxide, at a temperature between -7.degree. C. and 4.degree. C. The aqueous sodium hydroxide penetrates between the fiber layers. This extends the lattice structure and results in the formation of large, irregular distances therebetween. However, only the amorphous fraction of cellulose 1 fibers (e.g. about 20-30 percent) dissolves under these conditions.
Despite the fact that cellulose Q condition has been known for over 50 years, no one known to the present inventor has recognized the applicability of this technology to processing of sausage skins. Instead, as explained above, sausage skins stripped from sausages are wasted, typically either being sent to a landfill or incinerated.
Therefore, a need exists for an improved method of forming and processing sausage skins.